Protective device for electric circuits



Oct. 6,, 1925. 1,556,134

' E. R. STOEKLE fRO'l'lCTIVE bzvms FOR ELECTRIC CIRCUITS H196 Feb. 20. 1922 INVENTOR.

ATTORNEY Patented Oct. 6, 1925.

UNITED STATES 1,556,134 PATENT OFFICE.

IRWIN E. STOEKLE, 0'1 MILWAUKEE, WISCONSIN, LSSIGNOB TO THE CUTLER-HAM- m II'G. CO., 01' MILWAUKEE, WISCONSIN, A. CORPORATION OI WISCONSIN.

PROTECTIVE DEVICE FOR ELECTRIC CIRCUITS.

Application filed February 80, 1922. Serial No.,587,860.

To all whom it may concern:

Be it known that I, ERWIN R. STOEKLE, a citizen of the United States, residing at Milwaukee, in the county of Milwaukee and State of Wisconsin, have invented new and useful Im rovements in Protective Devices for Electric Circuits, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawing, forming a part of this specification.

This invention relates to protective devices for electric circuits, and more particularly to such devices involving in their action vaporization of a conductor which is li uid at working temperatures.

n my Patent No. 1,499,420, dated July l,

1924, is disclosed and claimed such a type of protective device having certain features in common with that herein contemplated.

In the construction and operation of such devices, articularly those designed to require vo untary resetting following operation thereof, great difficulty has heretofore been experienced in providing for effecting such resetting readily and positively without sacrificing some necessary or desirable o rative characteristic of the device, and t e present invention has as an object that of overcomin such difliculty.

Another ob ect is that of providing such a device adapted, followin operation thereof, to maintain the contro led circuit positively interrupted pending voluntary resettin and also to enable accomplishment of suc resetting action with ease and certainty.

Another object is that of simplifying and improving enerall the construction and operation 0 such evices.

Other objects and advantages will hereinafter appear.

In the accompanying drawing,-

Figure 1 is a vertical sectional view of a form of the apparatus embodying the in- -vention, certain circuit connections being illustrated diagrammatically; while,

Fig. 2 is a diagrammatic view including modified circuit connections adapting the device to aslightly different character of control. n

Referring to Fig. 1 of the drawing, the same illustrates a thermally responsive overload circuit interrupter requiring voluntary resetting and comprising an insulating and heat absorbent support 5, which may be similar to and standard with the corre sponding element of my patent aforementioned, said support having a heating coil 6 associated therewith and being internally provided with a longitudinal passage 7.

A thermally responsive circuit control element is carried wlthin said assage 7 and within the heating coil 6 su stantially as illustrated. Said element comprises a tube 8 of glass, or other suitable insulating material, closed at its lower end and outwardly flared at its upper end substantially as illustrated, said tube being of relatively large internal diameter and being preferably internally unconstricted. A conductor 9 is sealed within the lower end of the tube and connected with an electrode 10 located within the tube and extending upwardly within the space surrounded by the coil 6.

A reciprocable plunger 11, of conductive material, is arranged wlthin the upper portion of the tube 8 and spaced upwardly above the electrode 10 substantially as illustrated, said plunger having a bore 12 extending from the bottom thereof to a point considerably above the upper end of the tube 8 when the plunger is assembled, and said bore having at its upper end one or more openings leadin outside said plunger.

Said plunger is urthermore provided with an enlargement 13 located substantially as illustrated and preferably provided with a downwardly tapered conlcal surface substantially conforming to the contour of the adjacent flared portion of the tube 8 and bein ada ted to coact therewith in the manner of a valve with itsseat, suitable acking 14 of asbestos or other material Being preferabl interposed for purposes hereinafter set orth.

A conductive cap 16 is cemented or otherwise permanentl secured upon and about the upper end 0 the tube 8 in a manner to provide a chamber 17 in communication with the interior of said tube and also with the bore 12 substantially as illustrated; Said cap 16 is provided with an axial 0 ening through which the upper portion 0 the plunger 11 is adapted to extend, making therewith a sliding fit.

The upper end of the enlarged portion of said plunger is preferably provided with an upwardly facin annular shoulder 18, whereas a helica spring 19 is compressed tube and between said shoulder and the adjacent portions of the cap 16 and serves under normal conditions to maintain the plunger in its lowermost position with the valve in engagement with its co-operating seat.

The space within the tube 8 not occupied by the aforedescribed parts is filled with a conductive medium, indicated at 20, which -is liquid at working temperatures, such for example as metallic mercury, said conductor being adapted to extend slightly above the upper portion of the tube and within the aforedescribed recess 17 However, the free surface 21 of such conductor is to be maintained under all conditions below the level of the passages connecting the bore 12 with such recess. The stem of the plunger 11 is provided exteriorly of the cap 16 with an insulating knobor operating handle 22. The circuit to be controlled is caused to include the liquid conductor 20 aforementioned as by connecting one side of the circuit through terminal 23 which is connected with spring clip 24 and thence to conductor 9. The opposite side of the circuit is connected through terminal 25 and spring cup 26 to the cap 16 as illustrated. The heating coil 6 is connected in the circuit in accordance with an electrical condition of which it is desired that the aforementioned circuit .be controlled. Obviously the foregoing circuits may be the same or may be distinct.

In the operation of the device, so long as the current in the coil circuit does not exceed a given value, the heat evolved by said coil is absorbed and dissipated by the sup-- port with sufiicient rapidity to prevent operation of the device for interrupting circuit. However, upon a given value of brief overload or upon a lesser value of more prolonged overload, the heating effect of said coil is sufficient to effect vaporization of an intermediate portion of the liquid conductor located between the two electrodes aforedescribed whereupon the portion of said conductor located above such vaporized portion is expelled with great rapidity uiwardly through the bore 12 into the recess 1 of cap 16, thereby suddenly interrupting the controlled circuit between fluid contacts, automatic re-establishment of said circuit being prevented due to the aforementioned fact that the upper end of the external openings of said bore 12 are located above the level which the conductive liquid within the recess can attain, the valve 13 serving also to prevent reflux of the liquid.

If now the plunger 11 be lifted by means of the knob 22 against the force of spring'19, theyalve is opened, permitting ready and coplous reflux of liquid within the tube by means of the annu ar space between said plunger, such passage being independent o the bore 12, whereby any gaseous or vaporous matter located within the tube ductor which is liqui is readily displaced by the inflowing liquid with the result that such reflux of the latter is facilitated and expedited. Obviously such reflux of the liquid serves to reset the device which is thus rendered agaln active for completing the circuit subject to subsequent re-interruption upon the occurrence of overload.

It is of course to be understood that in gcneral the diameter of the bore 12 will be materially less than that of the individual bubbles of vapor of the liquid which form due to heating by the coil 6, thereby preventing free boiling of the liquid conductor and providing substantially explosive action for circuit interruption as aforedescribed. Thus the size of said bore best adapted to provide the foregoing effects is ordinarily too small to permit resetting of the device by reflux of conductive liquid through the same passage with the facility and certainty herein required. However, provision of the aforedescribed enlarged reflux passage provides'amply for such resetting. Moreover, provision of the valve 13 normally closing said reflux passage and also the aforedescribed arrangement whereby the upper end of the bore 12 is at all times above the free surface of the conductive liquid within chamber 17 provides for positively preventing resetting of the device except by opening of said valve.

With the circuit arrangement illustrated in Fig. 1, the heating coil 6 is connected in the circuit of a motor 27 which is to be protected, the joint circuit of the motor and coil being controllable by means of an electroresponsive switch 28 having a closing coil 29 connected across the motor clrcuit through the circuit interrupting element aforedesc ribecl and also preferably through a suitable control switch 30 as illustrated.

Thus said heating coil is subjected to influence of the motor current for determining response of the circuit interrupting element, whereas in responding said element serves to open the energizing coil of switch 28 which thereupon opens and interru ts the common circuit of the motor and the eating coil. Obviously restarting may be thereafter effected by simply closin the switch 30, assuming the same to have een opened,

following resetting of the circuit interru t ingelement in the manner aforedescribe f It is of course to be understood that wherever desirable or necessary the heater coil may be connected in series with the circuit nterrupting element and with the translating device to be protected substantially as illustrated in Fig. 2, the circuit connections there illustrated being obvious.

What I claim as new and desire to secure by Letters Patent is:

1. A circuit interru ter comprising a conatworking temperatures, electro-thermic means including an external heater for subjecting said conductor to fluid pressure of its own va or to effect sudden interruption of circuit t rough said conductor and means requirin operation thereof to efiect restoration of circult.

2. A circuit interrupter com rising a conductor which'is liquid at wor in temperatures,'electro-ther1nic means inc uding an external heater for eflecting sudden interruption. of circuit through said conductor, and 'means, including a voluntarily operable valve, requiring operation thereof to efl'ect restoration of circuit.

3. A circuit interrupter comprising a con ductor which is liquid at working temperatures, a support for said conductor providing for connection thereof in the circuit to be protected, electro-thermic means for subjecting said conductor to fluid pressure of 1ts own va r for interruption of circuit therethro'u h andmeans requiring voluntary actuation t erect to efl'ect restoration of circuit, said latter means including a passage for influx of said liquid within said support and a valveto control said passage.

4. A circuit interru ter comprising a conductor which is liquid at working temperatures, a support for said conductor providing for connection thereof in the circuit to be rotected, electro-responsive means for subjecting said conductor to fluid pressure of 1ts own vapor for effecting displacement of liquid of said conductor, subject to an inverse time element, for rendering the latter electrically discontinuous, means providing against automatic restoration of continuity 0 said conductor and voluntarily operable means providing for replacement of a like quantity of liquid for restoring continuity of said conductor, said support and said latter means having associated parts roviding difierent passages for such disp acemenlt and replacement of the liquid respective y.

5. In a protective device for electric circuits, the combination with a tubular insulatin support, of a conductor which is liqui at working temperatures to be carried by said support, means for subjecting said conductor to fluid flpressure of its own vapor to cause sudden e ux of liquid of said conductor from said support for rendering the conductor electrically discontinuous, a member. extending within said support provid ing a passage for such efilux of liquid and to prevent automatic reflux thereofand means for moving said member relatively -sulating support arranged vertically and having a flared upper end providing a valve seat, of a tubular electrode extending downwardly in said support, a conductor which is liquid at working temperatures to be contained in said support, means for subjecting said conductor to fluid pressure of its own vapor to cause a sudden upward flow of liquid of said conductor through said electrode for rendering said conductor electrically discontinuous, said electrode having parts to prevent return of liquid therethrough and being spaced from the interior of said tube to provide for return flow of liquid, a valve associated with said electrode to coact with said seat for controlling such return flow of liquid, means tending to maintain said valve closed and means providing for voluntary openin of the valve. 7. In a protective device for electric circuits, the combination with an insulating and heat absorbent base and a tubular electric heating element associated therewith, of a thermally res onsive circuit interruptin element insertab e within said base and sai heating element for support by the former in a vertical position, said element compris: ing an insulating tube having an electrode sealed within its lower end for exterior circuit connection, a terminal clip for said electrode carried by said base for positioning said tube therein, a tubular electrode penetrating the upper end of said tube, a conductive cap sealed about the upper end of said tube and electrically connected with said upper electrode, a conductor which is liquid at working temperatures carried within said tube in contact with said electrodes, said heatin element andsaid base providing for sub ection of said conductor to fluid pressure of its own vapor to cause sudden expulsion of liquid from said tube for rendering the conductor electrically discontinuous subject to an inverse time element, said upper electrode andsaid tube having parts providing a must automatic reflux of the expelled liqui and voluntarily operable means associated with said upper electrode to provide-for reflux of such liquid within said tube.

In witness whereof, I have hereunto subscribed my name.

ERWIN R. STOEKLE. 

